The present invention relates to a transgenic animal model for studying heart failure. In particular, the present invention relates to methods of studying molecular/cellular events associated with congestive heart failure, of testing drug candidates for prevention or treatment of congestive heart failure, of studying the effects of factors such as diet or exercise on congestive heart failure, and of studying specific conditions or diseases associated with congestive heart failure.
A variety of human diseases and conditions which are manifested by cardiac abnormalities or cardiac dysfunction can lead to heart failure. Heart failure is a physiological condition in which the heart fails to pump enough blood to meet the circulatory requirements of the body. The study of such a condition in genetically diverse humans is difficult and unpredictable. Therefore, there is a need for a model system which facilitates the study of the mechanisms and causes of heart failure as well as the identification of potential therapeutic targets.
The development of transgenic animal technology has provided significant advances for obtaining more complete information about complex systems in vivo. By manipulating the expression of gene(s) in vivo, it is possible to gain insight into the roles of such genes in a particular system or to study aspects of the system in a genetically controlled environment. Although cardiac disease in a small mammal is inherently different from that seen in humans, mammals such as the mouse allow analysis of disease at molecular and cellular levels that is often impossible in humans.
Accordingly, it is an objective of the present invention to provide a transgenic model system for the study of heart failure and methods of use thereof.
One embodiment of the present invention is a transgenic mouse which is a model for studying congestive heart failure. Such a transgenic mouse has incorporated into its genome a transgene which includes: (a) a heart tissue-specific promoter; and, (b) a nucleic acid sequence encoding an amino acid sequence of a xcex1 myosin heavy chain protein. The nucleic acid sequence has a first mutation comprising a point mutation which results in an Arg403Gln mutation in the amino acid sequence, and a second mutation comprising an interstitial deletion in a portion of the nucleic acid sequence that encodes an actin binding domain. The transgene is expressed in the heart tissues of the transgenic mouse.
Another embodiment of the present invention relates to a transgenic mammal which is a model for congestive heart failure. Such a transgenic mammal has substantially the same transgene incorporated into its genome as is described above for a transgenic mouse of the present invention.
Yet another embodiment of the present invention relates to a recombinant nucleic acid molecule which includes a nucleic acid sequence encoding an amino acid sequence of an xcex1 myosin heavy chain protein, such nucleic acid sequence being operatively linked to one or more expression control sequences. The nucleic acid sequence has a first mutation comprising a point mutation which results in an Arg403Gln mutation in the amino acid sequence and a second mutation comprising an interstitial deletion in a portion of the nucleic acid sequence that encodes an actin binding domain.
Yet another embodiment of the present invention relates to a method for studying the molecular and cellular events associated with congestive heart failure comprising the steps of: (a) harvesting cells and tissues from a transgenic mouse of the present invention as described above; and, (b) comparing the cells and tissues from the transgenic mouse to cells and tissues from a mouse which does not carry the transgene in an assay. Such an assay is selected from the group of morphological examination of cardiac cells; histological examination of coronary vessels; histological examination of heart sections; histological examination of myocytes; histological examination of myofibrils; evaluation of cardiac myocyte DNA replication and expression; evaluation of cardiac-related enzyme activity; and evaluation of apoptosis of cardiac cells.
Another embodiment of the present invention relates to a method to identify compounds for treating congestive heart failure. Such a method includes the steps of: (a) administering a compound to be evaluated to a transgenic mouse of the present invention as described above; and, evaluating physiological and pathological changes in the transgenic mouse compared to a mouse that did not receive the compound to determine the efficacy of the compound for treating congestive heart failure.
Yet another embodiment of the present invention relates to a method for evaluating the effects of external factors selected from the group of diet and exercise on congestive heart failure. Such method includes the steps of (a) establishing a normal control regimen for an external factor in a first transgenic mouse of the present invention as described above; (b) modulating the regimen for the external factor in a second transgenic mouse of the present invention as described above; and (c) monitoring the second transgenic mouse for a change in a characteristic associated with congestive heart failure compared to the first transgenic mouse.
Another embodiment of the present invention relates to a method to study the molecular and cellular events connected with a condition associated with congestive heart failure. Such a method includes the steps as described above for the method to study the molecular and cellular events connected with congestive heart failure. Such a condition or disease includes, but is not limited to dilated cardiomyopathy, hypertrophic cardiomyopathy, acute aortic regurgitation, tricuspid stenosis, constrictive pericarditis, acute infective endocarditis, ischemia heart disease, hypertension, primary myocardial disease, valvular disease, pericardial disease, hyperthyroidism, anemia, arteriovenous fistula, beriberi and Paget""s disease.
Another embodiment of the present invention relates to a method to produce a transgenic mouse which is a model for heart failure. Such a method includes the steps of (a) producing a first transgenic mouse of the present invention as described above; (b) producing a second transgenic mouse having incorporated into its genome a transgene comprising a nucleic acid sequence encoding a protein selected from the group of a protein involved in the angiotensin system, a protein involved in the xcex2 adrenergic pathway and a protein involved in calcium handling systems; and (c) breeding the first transgenic mouse with the second transgenic mouse to produce a third transgenic mouse that is useful for studying heart failure. In a preferred embodiment, the second transgenic mouse has a transgene encoding a xcex21-adrenergic receptor.
Yet another embodiment of the present invention relates to a method to produce a transgenic mouse that is a model for studying congestive heart failure. Such a method includes the steps of (a) introducing into an embryonic cell of a mouse a transgene as described previously herein; and (b) obtaining progeny having the transgene stably incorporated into the genome, such transgene being expressed in the heart tissues of the progeny. Such a method can further include step (c) of selecting male transgenic progeny, and further include the step of selecting male transgenic progeny that are at least about 5 months of age.
Another embodiment of the present invention relates to a transgenic mouse that is a model for hypertrophic cardiomyopathy. Such a mouse has incorporated into its genome a transgene comprising (a) a heart tissue-specific promoter; and, (b) a nucleic acid sequence encoding an amino acid sequence of a xcex1 myosin heavy chain protein. The nucleic acid sequence has a first mutation comprising a point mutation which results in an Arg403Gln mutation in the amino acid sequence and a second mutation comprising an interstitial deletion in a portion of the nucleic acid sequence that encodes an actin binding domain. The transgene is expressed in the heart tissues of the transgenic mouse at a level sufficient to promote hypertrophic cardiomyopathy in the mouse. In this embodiment, such a transgenic mouse is preferably a female transgenic mouse, or a male transgenic mouse that is at least less than about 8 months of age.